a senior israeli official says israel is ready for a ground invasion and president obama says israel has a right to defend itself but is warning against an invasion. >> israel has a new tool in the multilayer defense system. as chip reid reports, it's credited with saving countless lives. >> reporter: in six days of fighting, roughly 850 rockets have been fired at israel from gaza. more than 300 of them interce intercepted by this. the iron dome, israel's home-grown defense shield. operational since last year, the system is designed to protect populated areas allowing nonthreatening short range missiles to drop into opening fields or water and intercepting those headed for cities or towns. >> the iron dome has certainly been successful and given the israelis some strategic breathing space to be able to react upon their own timing and their own calculations. >> reporter: once hamas launches a missile from gaza israeli ground radars detect and track its path, relayed to a command and control center which launches the enter separate tore missile. within seconds, if all goes as planned,